Fused electric plug



Dec. 27, 1955 C. E. MASON FUSED ELECTRIC PLUG Filed Dec. 50, 1954 INVENTOR.

E. MASON nited States Patent FUSED ELECTRIC PLUG Charles E. Mason, Drexel Hill, Pa. Application December 30, 1954, Serial No. 478,763 2 Claims. (Cl. 200-4155) My invention is an improved fused electric plug. It is particularly useful in connection with portable electric power tools such as electric drills.

The purpose of a fused electric plug is to provide means for protecting the power tool unit to which it is attached and to avoid disturbing the other units on the same electric circuit in the event that the power tool should draw excess current. A short circuit or other condition causing large amounts of current to be drawn by the unit will cause one or both of the fuses in the plug to be blown thereby cutting off the power tool from the circuit and thus prevent blowing of the main fuses or tripping of a main circuit breaker. Heretofore, fused electric plugs have generally required special sockets, such as shown in my Patent No. 1,813,582, and they were frequently large and rather heavy. In some cases they could not be readily used in gangs. My new improved plug is of light weight construction and of minimum length and can be readily used in any conventional outlet either singly or in gangs.

The primary object of my invention is to provide a fused electric plug of the shortest possible length using standard size, cartridge type fuses.

A further object of my invention is to provide a fused type plug with a shell which may be readily adapted for use in either a two wire or a three wire system.

A further object of my invention is to provide a fused electric plug which may be used in standard outlets.

A further object of my invention is to provide a fused electric plug of light weight construction which may be used in groups of two or more.

A still further object of my invention is to provide a short, light weight, fused electric plug which can be readily adapted for use with a grounding wire.

In the drawings Fig. l is a side elevational view, in partial section, of my improved fused plug;

Fig. 2 is a bottom plan view of my improved fused plug, in partial section, taken along line 2-2 of Fig. 1;

Fig. 3 is a perspective view of the lower half of my improved fused plug when the shell is separated into two parts; and

Fig. 4 is a perspective view of the upper half of my improved fused plug when the shell is separated into two parts.

My fused electric plug comprises a shell 1 divided into an upper, cord receiving half 2 and a lower, pronged half 3 joined together by a bolt 4 and a barrel nut 5. Parallel bores 6 and 7 are provided in the upper and lower halves 2 and 3 and extend substantially throughout the length of the shell for the reception of cartridge fuses 8 and 9. Resilient sockets 10, 11, 12 and 13, by which the cartridge fuses are resiliently held within the bores 6 and 7, are seated in the ends of the bores 6 and 7. External prongs 14 and 15 mounted in the recess 16 formed in the lower end of the lower half 3 of the shell are electrically connected to the sockets 10 and 11, respectively, by means of rivets 17 and 17a.

Extending from the resilient sockets 12 and 13 to the large recess 18, formed in the upper half 2 of the shell, are conductors 19 and 20 which are bent over to form flanges 21 and 22 which rest upon the floor 23 of the recess 18 and overlie small bore recesses (not shown) extending from the recess 18 toward the closed end 24 of the upper half of the shell. Terminal screws 25 and 26 have their threaded ends projecting through apertures in the flanges 21 and 22 for engagement with nuts seated in said small bore recesses.

An aperture 27 for carrying an electric cord 28 extends from the end 24 of the shell to the large recess 18, the aperture being on that side of the shell opposite to that in which the terminal screws 25 and 26 are located. The longitudinal axis of the aperture 27 is parallel to but spaced from the longitudinal axes of the bores 6 and 7. The ends of the wires 29 and 30, carried within the cord 28, are secured to the flanges 21 and 22 by means of the terminal screws 25 and 26 and are thereby electrically connected to the external prongs 14 and 15 by means of the conductors 18 and 19, the sockets 12 and 13, the fuses 8 and 9, the sockets 10 and 11 and the rivets 17 and 17a.

The central location of the terminal screws 25 and 26 in the shell, within the overall length of the fuses 8 and 9, permits the plug to be of a length substantially shorter than that otherwise required.

The correct jointure of the two halves of the shell is assured by providing the lower half 3 with a large key boss 31 which projects beyond the face 32 and fits snugly within the perimeter of the large recess 18. That is to say, the key boss 31 has a wide land 33 near one side of the shell which land is joined by a neck 34 to a pair of lands 35 and 36 partially separated by a bay 37. The recess 18 has complementary bays 38, 39 and 40, to match the lands 33, 35 and 36 of the boss, and a complementary land 41 to fit within the bay 37 in the boss 31. By this arrangement the shell can be fitted together in but one direction only and the polarity of the plug cannot, therefore, be accidentally changed. The aperture 42 in the neck 34 extends through the lower half 3 of the shell and receives the bolt 4 and a portion of the barrel nut 5 by means of which the two halves are firmly held together.

Having described my invention, I claim:

1. A fused electric plug comprising a body portion formed of an upper half and a lower half of electric insulating material, a pair of fuse receiving bores extending substantially throughout the length of said upper and lower halves, spring sockets seated in the ends of said bores for engaging the ends of said fuses, a central aperture containing a nut and bolt for securing said upper half to said lower half, an aperture in said upper half parallel to but laterally displaced from the longitudinal axis of said fuse bores, a recess formed in the enclosed face of said upper half, a pair of terminal screws seated in said recess and electrically connected to the spring sockets in said upper half, an electric cord projecting through said aperture and connected to said terminal screws, and a pair of prongs extending from the bottom of said lower half and electrically connected to said sockets and cord.

2. A fused electric plug comprising a shell of electric insulating material formed of an upper half and a lower half, fuse receiving bores in said upper and lower halves, fuse sockets in the bottoms of said recesses, prongs projecting from said lower half and electrically connected to said sockets in said lower half, a key boss projecting from said lower half, a recess in the enclosed face of said upper half for receiving said boss, terminal screws seated in said recess, an aperture in said upper half extending to said recess for carrying an electric cord, means including said screws for electrically connecting said cord to said fuse receiving sockets in said upper half, and fastening means fol-securing said upper half to said lower half.

References Cited in the file of this patent UNITED STATES PATENTS 4 Keefe Sept. 30, 1941 Seurynck July 23, 1946 Shaul June 3, 1952 Eggers May 26,1953

FOREIGN PATENTS Great Britain Sept. 11, 1922 

